Liquid crystal display device

ABSTRACT

In order to avoid generation of black unevenness caused by the water intrusion into a liquid crystal display device, there is to provide a liquid crystal display device including a display area and a terminal portion, in which a TFT substrate with an organic passivation film formed, and an opposite substrate are adhered to each other by a seal portion and a liquid crystal is enclosed there, wherein in the seal portion of the TFT substrate, a groove-shaped through-hole is formed in the organic passivation film to surround the display area, a water absorption layer formed of the same material in the same process as that of the organic passivation film is formed within the groove-shaped through-hole, and the water absorption layer is not covered with the inorganic insulating film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/606,531 filed on May 26, 2017, which is a continuation of U.S. patentapplication Ser. No. 14/817,520 (now U.S. Pat. No. 9,696,592) filed onAug. 4, 2015. Further, this application claims priority from JapanesePatent Application No. 2014-160415 filed on Aug. 6, 2014, the contentsof which are hereby incorporation by reference into this application.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to a display device and particularly, to a liquidcrystal display device capable of avoiding black unevenness generated ina display area.

(2) Description of the Related Art

A liquid crystal display device is formed by a TFT substrate with pixelsincluding pixel electrodes and thin film transistors (TFT) formed in amatrix shape, an opposite substrate facing the TFT substrate, and aliquid crystal interposed between the TFT substrate and the oppositesubstrate. Then, an image is formed by controlling the transmittance oflight through liquid crystal molecules in every pixel.

In a liquid crystal display device, there sometimes occurs blackunevenness especially in the periphery of a display area. This may beaffected by the water entering into the liquid crystal. In order toavoid the water from entering inside, various structures have beendeveloped. On the other hand, there is another way of, even if waterenters into the liquid crystal display device, adsorbing the waterentered inside in order to suppress the affect on the liquid crystal.

Japanese Patent Publication Laid-Open No. 2008-191265 discloses astructure in which an adsorbent layer for adsorbing the water isarranged in a seal portion for sealing the TFT substrate and theopposite substrate. Japanese Patent Publication Laid-Open No.2012-150290 discloses a structure in which an adsorbent layer foradsorbing the water is arranged between a display area and a sealportion.

SUMMARY OF THE INVENTION

The both structures described in Japanese Patent Publication Laid-OpenNo. 2008-191265 and Japanese Patent Publication Laid-Open No.2012-150290 are to arrange an adsorption layer for adsorbing the waterentered inside a liquid crystal display device; then, as the adsorptionlayer, a material which is not used usually for the liquid crystaldisplay device is used. In other words, something other than theessential material for the operation of the liquid crystal displaydevice is used as another component. This conventional method has thefollowing problems:

(1) The other component is arranged in the different process; therefore,the manufacturing cost is increased according to an increase in thecomponent cost and the process. (2) The material other than theessential material for the operation of the liquid crystal displaydevice is used; therefore, it is necessary to check whether the displayperformance is affected by the material when the liquid crystal displaydevice is operated for a long time.

An object of the invention is to solve the above problems and to avoidblack unevenness from occurring in a liquid crystal display device byeffectively adsorbing water entered into a liquid crystal display panel,without increasing the manufacturing cost and without deterioratingreliability.

The invention is to solve the above problems and the concrete means areas follows.

(1) A liquid crystal display device including a display area and aterminal portion, in which a TFT substrate with an organic passivationfilm formed there and an opposite substrate are adhered to each other bya seal portion and a liquid crystal is enclosed there, wherein in theseal portion of the TFT substrate, a groove-shaped through-hole isformed in the organic passivation film to surround the display area, awater absorption layer formed of the same material in the same processas that of the organic passivation film is formed within thegroove-shaped through-hole, and the water absorption layer is notcovered with the inorganic insulating film.

(2) The device according to the above (1), wherein the water absorptionlayer is continuously formed along the whole periphery to surround thedisplay area.

(3) The device according to the above (1), wherein the water absorptionlayer is formed discontinuously to surround the display area.

(4) The device according to the above (1), wherein the water absorptionlayer is formed only in the corner portions of the display area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a liquid crystal display device accordingto the invention.

FIG. 2 is a cross-sectional view taken along the line A-A of FIG. 1.

FIG. 3 is an enlarged top plan view corresponding to FIG. 2.

FIG. 4 is an enlarged cross-sectional view of a seal portion of FIG. 2.

FIG. 5 is an enlarged cross-sectional view of another example of theseal portion of FIG. 2.

FIG. 6 is a schematic plan view illustrating the invention.

FIG. 7 is a schematic plan view illustrating another example of theinvention.

FIG. 8 is a schematic plan view illustrating further another example ofthe invention.

FIG. 9 is a cross-sectional view illustrating the structure of the sealportion of the liquid crystal display device used together with theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the embodiment of the invention, a structure foravoiding water from entering into a liquid crystal layer, which is usedtogether with the invention, will be described. FIG. 9 isacross-sectional view in the vicinity of a seal portion of a liquidcrystal display device. In FIG. 9, a TFT substrate 100 and an oppositesubstrate 200 are adhered to each other by a sealing material 20. Anorganic passivation film 4 serving also as a flattening film is formedon the TFT substrate 100. This organic passivation film 104 is formed ofacrylate resin; therefore, the above film absorbs water and transmitsthe water easily. Further, the organic passivation film 104 also servesas the flattening film and formed thick with 1 to 4 μm, generally with 2to 3 μm; therefore, the above film easily transmits the water.

The organic passivation film is provided with a groove-shapedthrough-hole along the end portion of the TFT substrate 100 in a way ofsurrounding a display area. The water absorbed by the organicpassivation film 104, coming from the end portion of the substrateinwardly, is shut out by the groove-shaped through-hole 1041 and doesnot arrive at a liquid crystal layer 300. In the groove-shapedthrough-hole 1041, the organic passivation film 104 is covered with theinsulating film 105 formed of SiN; therefore, it takes a long time forthe entered water to pass the groove-shaped through-hole 1041, hence toprolong a lifetime of the liquid crystal display device as much.

In the structure as illustrated in FIG. 9, however, once the waterpasses the insulating film 105, the water easily arrives at the liquidcrystal layer 300. According to the structure as illustrated in FIG. 9,there is a limit to a long life of the liquid crystal display device.

In the opposite substrate 200 in FIG. 9, a black matrix 201 is formedextensively in the end portion of the substrate. The black matrix 201 isformed of an organic material in many cases. When the black matrix isformed of the organic material, water easily enters from the endportion. In order to shut down the water entered through the blackmatrix 201, a black matrix groove 2011 is formed. The black matrix isnot so thick as the organic passivation film 104 in the TFT substrate100 and therefore, the entered amount of the water is smaller than thaton the side of the TFT substrate. The contents of the invention will bedescribed in detail using the following embodiments.

[First Embodiment]

FIG. 1 is a top plan view of a liquid crystal display device to whichthe invention is applied. In FIG. 1, the TFT substrate 100 and theopposite substrate 200 are adhered to each other by the sealing material20, with the liquid crystal interposed between the TFT substrate 100 andthe opposite substrate 200. The TFT substrate 100 is formed larger thanthe opposite substrate 200, and a portion of only one sheet of the TFTsubstrate 100 is a terminal portion 150. In the terminal portion 150, anIC driver 160 for driving a liquid crystal display panel and terminalsfor connecting a flexible wiring substrate for supplying power, videosignals, and scanning signals to the liquid crystal display panel areformed.

In FIG. 1, in a display area 500, scanning lines 30 respectively extendin a horizontal direction and are aligned in a vertical direction.Further, video signal lines 40 respectively extend in the verticaldirection and are aligned in the horizontal direction. An areasurrounded by the scanning line 30 and the video signal line 40 is apixel 35. In a narrow frame, a distance w between the end portion of thedisplay area 500 and the end portion of the liquid crystal displaydevice is small with about 1 mm. In this case, the width of the sealingmaterial becomes smaller and if so, the outside water gets easily reachthe liquid crystal layer in the display area. This easily causes aso-called black unevenness easily, affected by the water.

FIG. 2 is a detailed cross-sectional view of a seal portioncorresponding to the cross section taken along the line A-A of FIG. 1.In the seal portion illustrated in FIG. 2, the TFT substrate 100 and theopposite substrate 200 are adhered to each other by the sealing material20. In FIG. 2, the liquid crystal 300 is charged inside the sealingmaterial 20. In FIG. 2, a first insulating film 101 is formed on the TFTsubstrate 100 formed of glass. The first insulating film 101 can beoccasionally an undercoat film formed to prevent the impuritiesgenerated from the glass from contaminating the TFT semiconductor layer.A second insulating film 102 is formed on the first insulating film 101.The second insulating film 102 can be occasionally a gate insulatingfilm in the TFT. A scanning-line lead line 103 is formed on the secondinsulating film 102. The scanning-line lead line 103 shown in arectangular shape in FIG. 2 is a cross section of the scanning-line leadline 103, which is connected to the scanning line 30 in FIG. 1.

An organic passivation film 104 is formed to cover the scanning-linelead lines 103. The organic passivation film 104 is formed thick with 2to 3 μm, also serving as a flattening film. The organic passivation film104 is formed of photosensitive resin, which does not need photoresistfor patterning.

In the display area, it is necessary to connect a pixel electrode or acommon electrode formed on the organic passivation film 104 to a sourceelectrode of the TFT, which connection is performed through thethrough-hole formed on the organic passivation film 104. The organicpassivation film 104 is formed of resin such as acrylic resin. This filmeasily absorbs water and when the pixel electrode or the commonelectrode is formed directly on the organic passivation film 104, thepixel electrode or the common electrode is exfoliated especially in thethrough-hole portion, due to the water absorbed by the organicpassivation film 104. In order to avoid this phenomenon, theconventional art has been designed in that the diameter of thethrough-hole is enlarged so that the inorganic insulating film 105 maycover the organic passivation film assuredly, also in the through-hole.In other words, in the conventional art, it has been essential that theorganic passivation film 104 is covered with the inorganic insulatingfilm 105.

In FIG. 2, an interlayer insulting film 105 made of SiN is formed on theorganic passivation film 104. This interlayer insulting film 105 is aninsulating film between a lower layer electrode formed flat and an upperlayer electrode having a slit in the display area of the liquid crystaldisplay device of the IPS method. In some cases, the lower electrode maybe the common electrode and the upper layer electrode may be the pixelelectrode and in other cases, it may be reversed; the lower layerelectrode and the upper layer electrode are both formed of transparentoxide conductive film represented by Indium Tin Oxide (ITO).

Since the organic passivation film 104 easily transmits the water, asdescribed in FIG. 9, the groove-shaped through-hole 1041 is formed inthe organic passivation film 104 in order to shut out the water comingfrom the end portion through the organic passivation film 104. Thegroove-shaped through-hole 1041 is formed around the whole periphery ofthe TFT substrate 100 to surround the display area within the sealportion.

The characteristic of the invention is that a water absorption layer 10formed by the organic passivation film is formed in a shape of wallwithin the groove-shaped through-hole 1041, not covered with theinorganic insulating material. This water absorption layer 10 is toabsorb the water when water transmitted from the end portion of the TFTsubstrate 100 through the organic passivation film 104 further intendsto pass the groove 1041 of the organic passivation film 104. Accordingto this, a time from the intrusion of the water into the liquid crystaldisplay panel to the arrival at the liquid crystal layer 300 can beprolonged. As the result, a lifetime of the liquid crystal displaydevice can be prolonged.

In FIG. 2, an alignment film 106 is formed on the interlayer insultingfilm 105. The alignment film 106 is formed by applying an alignment filmmaterial that is originally liquid according to the flexography orinkjet, and three concave portions are formed on the organic passivationfilm 104 as a stopper so that the alignment film material does notarrive at the outer end portion of the seal portion. Further, thegroove-shaped through-hole 1041 formed further outside of the concaveportions also serves as the stopper against the alignment film material.In FIG. 2, the alignment film material passes over the three concaveportions and stops in the final convex portion.

In FIG. 2, a black matrix 201 is formed on the side of the oppositesubstrate 200. The black matrix 201 in FIG. 2 is provided in order toavoid light from leaking from the seal portion. The black matrix 201 isformed of resin and a black matrix groove 2011 is formed in order toshut down the water transmitted through the resin. A color filter 202 isformed on the black matrix 201 in a stripe shape in a direction verticalto the paper surface. The color filter 202 is formed correspondingly toa first column spacer 210 formed on an overcoat film 203.

The overcoat film 203 is formed on the color filter 202. The overcoatfilm 203 is provided with a convex portion in correspondence with theportion of the color filter 202. This convex portion is to avoid thealignment film material from spreading outside of the substrate whenapplying the alignment film material. The first spacer 210 is formed inthe convex portion of the overcoat film 203. The column spacer 210 is todefine the space between the opposite substrate 200 and the TFTsubstrate 100 in the seal portion.

In FIG. 2, a second column spacer 220 lower than the first column spacer210 is formed nearer to the side of the display area than the firstcolumn spacer 210. When a pressure is applied to the opposite substrate200 from the outside, the second column spacer 220 is to avoid the spacebetween the TFT substrate 100 and the opposite substrate 200 fromnarrowing excessively.

A wall spacer 250 is formed outside of the first column spacer. Thiswall spacer becomes the stopper against the alignment film. The wallspacer 250 is formed in two stages. The alignment film 106 is formed tocover the overcoat film 203. The outer shape of this alignment film ispartitioned by the wall spacer 250.

A bank-shaped spacer 230 is formed in the end portion of the sealportion. Production of the individual liquid crystal display panels isinefficient; therefore, a plurality of liquid crystal display panels areformed on a mother substrate to produce the liquid crystal displaypanels at once. In the mother substrate with the plural liquid crystaldisplay panels formed there, the bank-shaped spacer 230 is arranged inthe boundary of the liquid crystal display panels, scribing is performedalong the center of the bank-shaped spacer 230, and then, the substrateis cut into individual pieces of liquid crystal display panels. Whenthere is no bank-shaped spacer 230, this portion is the sealing material20 and when the sealing material 20 exists, even if scribing isperformed, it cannot be cut.

FIG. 3 is a top plan view corresponding to the portion of FIG. 2. InFIG. 3, the sealing material 20 is formed inside the bank-shaped spacer230. In FIG. 3, the color filter 202 is formed in a stripe shape and thefirst column spacer 210 is arranged in the portion corresponding to thecolor filter 202. In FIG. 3, the color filter 202 and the first columnspacer 210 are shown, by way of example, for two lines. The wall spacer250 is arranged between the first column spacer 210 and the first columnspacer 210. The sealing material 20 is formed extensively in the endportion of the bank-shaped spacer 230. In FIG. 3, the water absorptionlayer 10 is formed between the bank-shaped spacer 230 and the colorfilter 202 on the side of the TFT substrate.

FIG. 4 is a cross-sectional view enlarging the portion of the waterabsorption layer 10 in FIG. 2. In FIG. 4, the water absorption layer 10is formed in the portion of the groove-shaped through-hole 1041 of theorganic passivation film 104. This water absorption layer 10 is formedof the same material in the same process as that of the organicpassivation film 104; as the result, there needs no additional materialcost and process in order to form the water absorption layer.

The water absorption layer 10 is not covered with the inorganicinsulating film 105, differently from the organic passivation film 104in the other portion. Therefore, after completion of the liquid crystaldisplay device, it can absorb the water transmitted through the sealingmaterial 20. In FIG. 4, the width w1 of the water absorption layer 10is, for example, 30 μm and the height h is 2 to 3 μm. On the other hand,the width of the groove-shaped through-hole 1041 formed in the organicpassivation film 104 is about 70 μm. Here, these numeric values can beadjusted according to the water absorption effect expected by the waterabsorption layer. FIG. 5 is a cross-sectional view when the crosssection of the water absorption layer 10 is trapezoid; when the waterabsorption layer 10 is in this shape, the width w of the waterabsorption layer 10 can be measured only by the bottom of the trapezoid.Here, in the embodiment, the water absorption layer is not covered withthe inorganic insulating film, but apart thereof may be covered with theinorganic insulating film to expose the part from the inorganicinsulating film. Further, according to the water entering amount, in aplan view, the area of the portion exposed from the inorganic insulatingfilm may be partially various.

FIG. 6 is a top plan view only showing the shape of the water absorptionlayer 10 in the TFT substrate. As illustrated in FIG. 6, the waterabsorption layer 10 is generally formed in the whole periphery tosurround the display area 500. However, when the water absorption layer10 cannot be formed continuously in the periphery with regard to thelayer of the wiring, the above layer 10 may be formed discontinuously,as illustrated in FIG. 7. Especially, in the screen corners, when blackunevenness occurs on the screen, the water absorption layer 10 may beformed only around the corners, as illustrated in FIG. 8. Further, inFIGS. 6 to 8, the water absorption layer 10 is formed in a linear shapein a plan view; however, it is not restricted to this but may be formedin a wave shape or a zigzag.

As mentioned above, according to the invention, the water absorptionlayer 10 can be formed in the same material in the same process as thatof the organic passivation film 104; therefore, the black unevennessgenerated on the screen due to the water can be avoided without anincrease in the manufacturing cost.

What is claimed is:
 1. A display device comprising: a first substratehaving a first organic film, a second substrate opposed to the firstsubstrate and having a light shield film and a protrusion formed on thelight shield film, and a seal material bonding the first substrate andthe second substrate, wherein the protrusion comprises a firstprotrusion and a second protrusion which is separated from the firstprotrusion, the first protrusion and the second protrusion are formed ina line shape, and opposed to the first organic film, and the firstprotrusion and the second protrusion overlap with the seal material, ina plan view.
 2. The display device according to claim 1, wherein thefirst protrusion and the second protrusion does not contact with thefirst organic film.
 3. The display device according to claim 1, whereinthe second substrate has a second organic film which is formed betweenthe light shield film and the protrusion, the light shield film has aslit, and the second organic film is filled in the slit.
 4. The displaydevice according to claim 3, wherein the second organic film is anovercoat film, and covers the light shield film.
 5. The display deviceaccording to claim 1, wherein at least one of the first protrusion andthe second protrusion is overlapped with an orientation film.
 6. Thedisplay device according to claim 1, wherein the first organic film hasa first portion which is an edge of the organic insulation film that isformed in an entire display area, a second portion which is separatedfrom the first portion and a third portion, and the third portion isformed between the first portion and the third portion, the firstprotrusion and the second protrusion are opposed to the first portion.7. The display device according to claim 6, wherein the second portionis overlapped with an end of the first substrate.
 8. The display deviceaccording to claim 6, wherein the first substrate has an inorganic filmwhich is formed on the first organic film, the inorganic film covers thefirst portion.
 9. The display device according to claim 8, wherein theinorganic film covers the second portion, and does not cover the thirdportion.
 10. A display device comprising: a first substrate having afirst organic film, a second substrate, opposed to the first substrate,having a light shield film and a second organic film formed on the lightshield film, and a seal material bonding the first substrate and thesecond substrate, wherein the first organic film has a first portion, asecond portion, and a third portion, the first portion is formed in anentire display area, the second portion, separated from the firstportion and the third portion, is formed closer to an end of the firstsubstrate than the first portion and the third portion, the thirdportion, separated from the first portion and the second portion, isformed between the first portion and the third portion, the light shieldfilm has a slit, the third portion overlaps with the slit, in a planview, and the second organic film is filled in the slit.
 11. The displaydevice according to claim 10, wherein the second organic film is anovercoat film.
 12. The display device according to claim 10, wherein thefirst substrate has an inorganic film which is formed on the firstorganic film, the inorganic film covers the first portion.
 13. Thedisplay device according to claim 12, wherein the inorganic film coversthe second portion, and does not cover the third portion.
 14. Thedisplay device according to claim 10, wherein an end of the firstportion overlaps with the seal material, in a plan view, and the secondportion, and the third portion are covered by the seal material, in aplan view.